Alternating current brake motor



Feb. 15, 1949. J. H. NELSON ETAL ALTERNATING CURRENT BRAKE MOTOR 2Sheets-Sheet 1 Filed Feb. 26, 1945 xx 1 Mwfl m ww m 49 w 5 1/ w 1 v. 4 xJ m 1 Feb. 15, 1949. J. H. NELSON ET AL ALTERNATING CURRENT BRAKE MOTOR2 Sheets-Sheet 2 Filed Feb. 26, 1945 electrically actuated brakeconstruction.

I eral have 'vided for each pair of Patented Feb. 15, 1949 ALTERNATINGCURRENT BRAKE MOTOR and Hoyt Servis, Racine, Win,

James Holly Nelson 2,461,159 OFFICE auignora to The Dumore Company,Racine,

Wis

., a corporation of Wisconsin Application February 26, 1945, Serial No.579,788

This invention relates to alternating current brake motors, and inparticular, to an improved Direct current electric brake motors ingenbeen provided with spring actuated braking 'means which arerenderedineffective during energization of the'neld by means of anelectromagnet. In adapting such construction to alternating currentmotors, certain dinicuities are encountered in the construction of aproperly operating alternating current magnet.

One of the diiilculties is the hum or the chatter of the armature of thealternating current magnet. Another difficulty is the provision of acompact construction which will carry suillcient flux- ;to permit theuse of a relatively strong brake spring.

An object of this invention is to provide a compact construction inwhich the electromagnet surrounds the armature shaft and is providedwith a plurality of pairs of pole pieces which are circumferentlallyspaced from each other around a doughnut shaped winding.

Another object is to provide an armature construction in which aseparate armature is propole pieces, the separate armatures beingmounted so that each may seek its own attracted position, therebyreducing any tendency of the armature to hum. The separate armatures aresecured to one another by means of an additional element which forms apart of the brake.

The objection to the use of a common armature, for all of the separatepole pieces is that from a practical viewpoint it is impossible to forma laminated core structure in which the armature contacting surfaces ofthe pole pieces all lie in the same plane. For instance, if one of thepole pieces lies below the plane defined by the others, the alternatingflux will cause the common armature to flex or I to vibrate, therebycausing a hum. In the construction herein shown and described, a fluxcarrying member contacts each of the pole pieces whenever theelectromagnetic winding is energized.

A further object is to provide an improved arrangement of pole pieces,and of shading means therefor, thereby further reducing any tendency tohum.

Various other objects, features and advantages will become apparent asthis description proceeds.

With reference now to the drawings which illustrate a preferredembodiment of this invention, and in which like reference numeralsdesignate like parts, i

Fig. 1 is a section through a brake motor taken along line i-l of Fig.2;

Fig. 2 is a section taken along line 2-2 of Fig. 1, andshowing theconstruction of the electromagnet;

4 Claims. (cuss-1'11) field H, the armature shaftv i2, and is rigidly Imeans of a hub II. a

Fig. 3 is a section taken along line 3-3 oi. Fig. 1, and showing. theconstruction of the armature; and

Fig. 4 is an enlarged detailof the rivet by means of which the separatesecured to the armature assembly. 7

The numeral 10 designates a motor housing in which are disposed theusual armature II and being mounted on an armature shaft l2 which isjournaled in bearings A brake disk II is carried by the armatureassociated therewith by An electromagnet, and a cooperating armatureassembly designatedgenerally by the reference numerals l and II, aredisposed at one end of the housing In and surround the armature shafti2. The armature assembly 18 includes a plurality of brake shoes i9which are disposed in such a position that they cooperate with the brakedisk l5 being urged into engagement therewith by a plurality of springs20. The electromagnet ll is connected in series with the field I4 sothat upon energization of the motor, the armature assembly I8 isretracted against the bias of springs 20 thereby disengaging the brakedisk l5. Upon deenergization of the motor circuit, the armature assembly|8,is released and the brake shoes I! are thereupon urged intoengagement with the brake disk l5, thereby braking the motor.

The electromagnet ll includes a mounting plate 2| which is secured tolugs 22 by means of suitable screws 23, the lugs 22 preferably beingcast integrally with the housing I0. Four U-shaped core, members 24 aresuitably secured to the mounting ;late 2!, the ends of the core membersbeing bifurcated to provide a pair of inner pole pieces 25 and 26, and apairof outer pole pieces 21 and 28. A common shading ring 29 is disposedbetween pole pieces 25 and 26, thereby shading all of the pole ing rings30 are provided for each of the outer pole pieces 28. The core members24 may be of the usual laminated construction.

U-shaped core members 24, and the usual protective coverings 32 may beprovided between the winding and the core members. It'will be seentherefore that when the winding 3| is energized by an alternatingcurrent, flux will pass through the'core members 24, the flux of thepole pieces 25 and 28 lagging behind the flux of the pole pieces 28 and21 due to the shading.

The armature assembly l8 includes a plate 31 which is apertured for thearmature shaft l2 and which is non-rotatably mounted with respect to thehousing In and the electromagnet ll. The brake shoes l9 are secured toone surface of the plate 31. The springs 20 are confined between theplates 21 and 21.

armature pieces are 1 pieces 25. Separate shad- A doughnut shapedwinding 3i is placed in the The position of the springs 20 the armaturepieces about the is determined by posts 33 which may be riveted orotherwise secured to the plate 2|, and which extend through notches inthe .plate 3'! and serve to guide its motion toward and away from theelectromagnet, l6.

To the surface of the plate 31 which faces the electromagnet II aresecured a plurality of separate armature pieces by means of rivets H.The apertures in the armature pieces 40, through'which apertures therivets 4| pass, are somewhat larger than the diameter of the rivet so asto provide a clearance as indicated by the reference numeral 42 in Fig.4. The result of this construction is that the armature pieces areloosely mounted with respect to the plate 31, and are thereby permitteda certain amount of wobble. The inner ends of the separate armaturepieces 40 are so shaped that the edge of one armature piece abuts theedge of an adjacent armature piece. In order to prevent the rotation ofarmature pieces 40 in the plane in which they are disposed, interlockingmeans edges of the diflerent armature pieces are provided. Thisinterlocking means may comprise lugs 43 formed along one of the abuttingedges of each armature piece, and a corresponding recess 46 formed inthe other edge of each armature piece. The arrangement is such that thelug of one armature piece fits into the recess of an adjacent armaturepiece, and

rivets ll is prevented. It will be noted, however, that thisinterlocking arrangement places no restriction on the movement ofthe'armature pieces in a direction perpendicular to the plane of plate37.

Upon energization of the winding 3|, each armature piece. will beattracted separately by the pole pieces 25, 26, 21 and 28 of thecorrespondingly positioned core member 24. Thus the plate 31 is causedto be displaced axially against the compression of springs 20. As eacharmature piece 40 moves into attracted position, it is free to seek itsown limit of motion as determined by its cooperating pole pieces, oneend of the armature piece engaging pole pieces 25 and 26,

between the abutting.

therefore rotation of pieces, said separate armatures being secured tosaid braking element in a manner such as to permit a slight adjustmentin the position of each as each seeks its attracted position.

2. In an electric brake having an alternating current electromagnet,which magnet is provided with a plurality of circumferentially spacedpairs of poles, an armature construction comprising a disk having aplurality of separate armatures, each armature being loosely secured tosaid disk by means of a rivet, and the inner ends of said armaturesbeingin contact with each other and being provided with interlockingmeans so as to prevent rotation of the separate armatures about theirmounting rivets.

3. In an alternating current brake motor, the combination of an armatureshaft, a brake disk secured thereto and rotating therewith, an axiallydisplaceable braking element mounted for cooperation therewith, meansfor biasing said braking element into engagement with said brake disk, atoroidal winding surrounding said armature shaft adjacent said brakingelement, a plurality of U-shaped core members circumferentially spacedaround said winding, the end portions of each being provided with a pairof pole pieces, each pole'piece being slotted, a common shading ringsurrounding said armature shaft and received within the slots of theinner pole piece of each pair for shading the inner half of each of saidinner pole pieces, a separate shading ring received within the slots ofeach of the outer pole pieces of each pair for shading the outer half ofeach of said outer pole pieces, and an armature member provided for eachof said pairs of pole pieces, said winding being disposed adjacent saidbraking element, and said separate and the other end engaging polepieces 21 and 28.

Thus there is no armature hum which is ordinarily occasioned by theprovision vof a common armature for several pairs of poles, for thereason that there is no gap due to imperfect alignment of the polepieces. It will also be noted that the shaded poles 25 and 28 cause thearmature pieces to remain in attracted position during current reversalin the winding 31.

' Although only a preferred embodiment of this invention has been shownand described herein, it will be understood that various modificationsand changes may be made without departing from the spirit of thisinvention. The appended drawings and foregoing description are deemed tobe illustrative only, and the invention is limited only by the appendedclaims.

We claim:

I 1.-In an alternating current brake motor, the combination 0! anarmature shaft, a disk secured thereto and rotating therewith, anonrotatable braking element disposed adjacent said disk, means to urgesaid braking element into braking contact with said rotating disk, atoroidal electromagnetic alternating current winding surrounding saidarmature shaft and having a plurality of pairs of pole pieces associatedtherewith each pole piece of each pair being slotted, shading meansdisposed in said slots, and a separate armature in the form of a platefor each pair of pole armatures being loosely secured to said brakingelement to retract the same against the action of said biasing means.

4. In a brake motor of the type which includes a single alternatingcurrent electromagnet winding provided with a plurality of pairs of polepieces lying in substantially a common plane, an armature for each pairof pole pieces, a common mounting member, means forloosely securing eacharmature to said mounting member, said armatures being arranged so thatan edge of one abuts an edge of another, and a projection on theabutting edge of one armature which fits into a corresponding notch inthe abutting edge of the adjacent armature whereby rotation'of saidarmatures with respect to said common mounting means is prevented. i t

JAMES HOLLY NELSON. HOYT SERVIS.

REFERENCES CITED The following references are of record in the file ofthis patent:

UNITED STATES PATENTS

